Bobtail squid (order Sepiolida) are a group of cephalopods closely related to cuttlefish. Bobtail squid tend to have a rounder mantle than cuttlefish and have no cuttlebone. They have eight suckered arms and two tentacles and are generally quite small (typical male mantle length being between 1 and 8 cm).[1]

Sepiolida are iteroparous and a female might lay several clutches, each of 1-400 eggs (dependent on species), over her estimated one-year-long lifetime.[1] The eggs are covered with sand and left without parental care.[1] Symbiosis with A. fischeri from the surrounding seawater is initiated immediately upon hatching, and the bacteria's colonisation of the juvenile light-organ induces morphological changes in the squid that lead to maturity.[1]